Lespedeza Davurica Research Articles

Pollination Biology of Lespedeza davurica

Background: In order to reveal the pollination biological characteristics of Lespedeza davurica, wild L.davurica from eight regions of Shanxi Province was used as test materials to study their floral dynamic, pollen storage and other aspects.Methods: During 2019, the flowering dynamics of wild L. davurica collected from eight regions of Shanxi Province were observed by selecting the better-grown L.davurica. Freshly bloomed flowers were picked, and their pollen was set up for two treatments, dry and undried, for pollen storage experiments. Pollen viability was determined by the TTC (expand for first instance) and MTT (expand for first instance) methods and stigma receptivity was determined by the hydrogen peroxide-benzidine method.Result: The results showed us the following points: the flowers of L. davurica were pale yellow, large and fragrant; it usually opens from the base to the top with distinctly asymmetrical petals; it opens during the day and closes at night; the number of flowers reached its peak between 12:00 and 14:00. After measuring the pollen viability of L. davurica, we found that dry storage at -20°C was the most effective treatment. And with the increase of temperature and decrease of humidity, the pollen viability and stigma receptivity of L. davurica increased continuously and the highest viability value occurs between 12:00 and14:00.

Effect of seed size and fungicide on germination and survival of buried seeds of two grassland species on the Loess Plateau, China

Seed size has important fitness consequences that potentially extend throughout the life cycle of plants. However, the effect of variation in seed size on seed survival in the field is poorly understood. We used two grassland species Setaria viridis (physiological dormancy) and Lespedeza davurica (physical dormancy) to test the effect of within species seed size variation on seed germination, viability and susceptibility to pathogen attack in the soil. Seed bags with different sizes of seeds for each species were treated with fungicide or water (control) and buried for 4 months in the field on the Loess Plateau, China. We found that field germination of large seeds was consistently higher than that of small seeds for both species. Small seeds of S. viridis had higher field mortality than large seeds, but the mortality of seeds of L. davurica was not affected by seed size. More small than large seeds of L. davurica remained viable during field burial, but the viability of buried seeds S. viridis did not differ with size. Our study suggests that within species seed size can influence germination, mortality and viability of buried seeds in the soil, but seeds with different kinds of dormancy shows different patterns in the relationship between seed size and seed survival.

Effects of different seed coating formulations on seed germination and seedling growth of Lespedeza davurica

Effects of different seed coating formulations on seed germination and seedling growth of Lespedeza davurica

Different effects of sheep excrement type and supply level on plant and soil C:N:P stoichiometry in a typical steppe on the loess plateau

Deposition of urine and dung is a key mechanism by which herbivores influence the nutrient cycling of terrestrial ecosystems. Yet, little is known about the roles of urine, dung and their mixtures in regulating the plant and soil carbon:nitrogen:phosphorus (C:N:P) stoichiometry and their interactions. We explored how different excrement types (urine, dung and their mixtures) and supply levels [urine: 0.5, 1.0 and 1.5 L m−2; dung: 4.7, 9.4 and 14.2 g m−2; mixtures (urine+dung): 0.5 + 4.7, 1.0 + 9.4 and 1.5 + 14.2] altered the plant and soil C:N:P stoichiometry in a semi-arid grassland on the Loess Plateau. We found that the aboveground biomass of the whole community was highest at the highest mixtures application rate, while the highest aboveground biomass of the three dominant species was detected at applications of 0.5 L m−2 urine for Stipa bungeana, 9.4 g m−2 dung for Lespedeza davurica and 1.0 L m−2 urine +9.4 g m−2 dung for Artemisia capillaris. Urine and dung alone increased plant N concentration, which peaked at 1.0 L m−2 urine. Plant P concentration at 1.5 + 14.2 mixtures was significantly higher than that at control without significant difference between excrement types. Compared to the control, excrement deposition did not significantly change plant C concentration and C:N, C:P and N:P ratios. However, plant C:P and N:P ratios under the mixtures were significantly lower than those under urine or dung. Excrement applications led to more soil (total, microbial and organic) C, N and P accumulations. Compared to urine and dung, the mixtures induced higher total P concentration but lower total N concentration in soil. Our study demonstrated that the impacts of sheep urine and dung on plant and soil C and nutrient concentrations and stoichiometry differed from that of mixtures. The plant N:P ratio indicated balanced N:P supply for urine and dung applications but N limitation for mixtures application. This study provides experimental evidence that the excrement of herbivores plays an important role in altering ecological stoichiometry in plants and soil.

Root growth and morphology of switchgrass (Panicum virgatum L.) and bushclover (Lespedeza davurica S.) in mixed plantation under varying soil water and phosphorus supply conditions

Root growth and morphology of switchgrass (Panicum virgatum L.) and bushclover (Lespedeza davurica S.) in mixed plantation under varying soil water and phosphorus supply conditions

Effects of nitrogen addition and planting density on the growth and biological nitrogen fixation of <i>Lespedeza davurica</i>

Effects of nitrogen addition and planting density on the growth and biological nitrogen fixation of <i>Lespedeza davurica</i>

Aboveground biomass production and dominant species type determined canopy storage capacity of abandoned grassland communities on semiarid Loess Plateau

AbstractQuantifying canopy storage capacity and its temporal variation is necessary for evaluating the ecohydrological effects of grassland restoration. In this study, four grassland communities after abandonment of 2, 7, 15 and 30 years on the semiarid Loess Plateau were selected, and canopy storage capacities, canopy structures and species compositions were examined in the growth period (May to September). Canopy, living plant, standing litter and floor litter storage capacities ranged from 0.11–0.56, 0.030–0.51, 0.0070–0.079 and 0.013–0.21 mm, respectively, and all exhibited an increasing trend with restoration year. Canopy storage capacity, vegetation coverage and aboveground biomass reached the maximum in August. Standing and floor litter storage capacities had the highest correlations with their biomass weights. Species diversity reached the maximum in 15 years abandoned grassland, with no significant monthly change. Annual forb, annual grass, perennial forb and perennial forb/grass were the typical dominant species type of 2, 7, 15 and 30 years abandoned grasslands, respectively. Perennial forbs (Artemisia gmelinii, Lespedeza davurica) had higher water storage than those of annual forb (Artemisia capillaris) and grasses (Setaria viridis, Roegneria kamoji). Path analysis revealed that fresh aboveground biomass and dominant species type mainly affected canopy storage capacity. No significant correlations were found between storage capacity and species diversity indexes. These results highlighted the importance of vegetation aboveground biomass and species functional group for evaluating grassland hydrological function and adopting suitable restoration strategy.

Identification of the important environmental factors influencing natural vegetation succession following cropland abandonment on the Loess Plateau, China.

Identification of typical vegetation succession types and their important influencing factors is an important prerequisite to implement differential vegetation and soil management after land abandonment on the Loess Plateau, China. However, there is no reported study specifically on the identification of vegetation types and their important factors as well as the thresholds of the important factors for classification of the vegetation types, based on the medium- to long-term succession of natural vegetation after cropland abandonment. We collected vegetation and soil data on the natural vegetation with the longest 60-year-old forest communities that developed after cropland abandonment and analyzed the data using two-way indicator species analysis, detrended correspondence analysis, direct canonical correspondence analysis and classification tree model. The vegetation communities were classified into five distinct vegetation types, including Artemisia scoparia, Lespedeza davurica and Stipa bungeana, Artemisia giraldii pamp, Sophora viciifolia, Quercus liaotungensis and Biota orientalis. The years after cropland abandonment and soil C/N were further identified as important factors determining the types of vegetation. Likewise, it was observed that most of the investigated soil nutrient variables and soil texture-related variables improved with the vegetation succession while soil water in the surface layers showed a decreasing trend. These findings may provide an ecological basis for site-specific management of vegetation types after cropland abandonment in the medium-long term on the Loess Plateau. Our results encourage further exploration of vegetation succession and their important factors based on longer periods of vegetation succession after cropland abandonment under more soil and climatic conditions on the mountainous areas as the Loess Plateau.

Growth Indicators of Main Species Predict Aboveground Biomass of Population and Community on a Typical Steppe.

The objective was to explore a fast, accurate, non-destructive, and less disturbance method for predicting the aboveground biomass (AGB) of the typical steppe, by using plant height and canopy diameter of the dominant species, Stipa bungeana, Artemisia capillaris, and Lespedeza davurica, data were observed from 165 quadrats during the peak plant growing season, and the product of plant height (PH) and canopy diameter (PC) were calculated for each species. AGB of population were predicted for the same species and other species through using 2/3 of the measured data, and the optimal predictive equation was linear in terms of determination coefficient. The other 1/3 of the data, which was measured from no grazing paddocks or rotational grazing paddocks, was substituted into the predictive equations for validation. Results showed that PC of one dominant species could be used to predict AGB of the same species or other species well. The predicted and measured values were significantly correlative, and most of the predictive accuracy was above 80%, and not affected by managements of grassland, including rotational grazing or no grazing. A combination of 3 to 6 representative species was used to predict AGB of the community, and the predictive equations with PC of six species as an independent variable were the most optimal because explaining 83.5% variation of AGB. The predictive methods cost 1/15, 1/9, and 1/51 of time, labor, and capital as much as the destructive sample method (quadrat sampling method), respectively, and thus improved the efficiency of field study and protecting the fragile study areas, especially the long-term study sites in grassland.

Photosynthesis and nutrient-use efficiency in response to N and P addition in three dominant grassland species on the semiarid Loess Plateau

Understanding the ecophysiological and nutrient-use strategies of dominant species is important for clarifying plant growth and an ecological process in their community under unbalanced N and P inputs. This study investigated effects of N and P addition [main plot: 0, 25, 50, and 100 kg(N) ha-1 year-1; subplot: 0, 20, 40, and 80 kg(P) ha-1 year-1] on leaf N and P contents (LNCa and LPCa), photosynthetic capacity (PNmax) and photosynthetic N- and P-use efficiencies (PNUE and PPUE) in three species (Stipa bungeana, Bothriochloa ischaemum, and Lespedeza davurica) in a semiarid grassland in China. At the assessing time, N addition alone significantly increased LNCa and LNCa/LPCa ratio of Stipa bungeana (C3 grass) only, while PNmax increased significantly in all three species. Under N addition, P addition caused significantly lower LNCa, but higher PNUE and PNmax in Bothriochloa ischaemum (C4 grass) and Stipa bungeana. The LNCa, PNmax, and PNUE of Lespedeza davurica (C3 legume) increased significantly after P addition regardless of N application. The LNCa/LPCa for optimum PNUE changed with species. The PNmax and PNUE of Bothriochloa ischaemum and Stipa bungeana had a peak when LNCa/LPCa attained ~ 11 and ~ 20. Lespedeza davurica tended to retain greater PNmax and PNUE at lower LNCa/LPCa. Our results indicated that the C3 grass was more sensitive to N and P addition than the C4 grass and the C3 legume in terms of leaf N and P contents and PNmax. Such interspecific variations of nutrient use in response to N and/or P addition are favorable for maintaining the diversity and the stability of the grassland community.

Response of runoff and soil erosion to erosive rainstorm events and vegetation restoration on abandoned slope farmland in the Loess Plateau region, China

It has been widely known that vegetation restoration plays a vital importance in controlling surface runoff and soil erosion. The most of soil erosion were caused by erosive rainstorm events. Yet, the response of surface runoff and soil erosion to erosive rainstorm events and vegetation types has not been fully understood. In this study, we monitored the vegetation, rainfall, runoff and soil erosion on ten runoff plots under field conditions from 2015 to 2019 and examined the impact of erosive rainstorm events on runoff and soil erosion among different vegetation types (Artemisia scoparia → Stipa bungeana → Lespedeza davurica (Asc → Sb → Ld), Stipa bungeana → Artemisia gmelinii (Sb → Agm), Bothriochloa ischaemum (Bi), Artemisia gmelinii + Stipa bungeana (Agm + Sb), Artemisia gmelinii + Stipa grandis (Agm + Sg), Sophora viciifolia (Sv), Artemisia gmelinii + Artemisia giraldii (Agm + Agi)) and bare land on abandoned land slopes. The results showed that vegetation restoration could decrease 68.0% to 97.4% of runoff and 98.0% to 99.9% of soil erosion compared to the bare land and there were no significant difference of surface runoff and soil loss among different vegetation types under the 11 erosive rainstorm events. The average soil loss of erosive rainstorm events among vegetation types could be 2.1 to 15.6 times as those of ordinary erosive rainfall events. The erosive rainstorm events caused a significant variance of surface runoff and soil erosion because of variant antecedent soil moisture and rainfall intensity. In practice, the natural vegetation restoration should be recommended in semi-arid environment and, the erosive rainstorm events should be paid enough attention in causing intense soil erosion in the rainy reasons.

Changes in levels of enzymes and osmotic adjustment compounds in key species and their relevance to vegetation succession in abandoned croplands of a semiarid sandy region.

Reclamation of cropland from grassland is regarded as a main reason for grassland degradation; understanding succession from abandoned cropland to grassland is thus crucial for vegetation restoration in arid and semiarid areas. Soil becomes dry when cropland is reverted to grassland, and enzyme and osmotic adjustment compounds may help plants to adapt to a drying environment. Croplands that were abandoned in various years on the Ordos Plateau in China, were selected for the analysis of the dynamics of enzymes and osmotic adjustment compounds in plant species during vegetation succession. With increasing number of years since abandonment, levels of superoxide dismutase increased in Stipa bungeana, first decreased and then increased in Lespedeza davurica and Artemisia frigida, and fluctuated in Heteropappus altaicus. Levels of peroxidase and catalase in the four species fluctuated; levels of proline, soluble sugar, and soluble protein either decreased or first increased and then generally decreased. According to a drought resistance index, the drought resistance of the four species was ranked in descending order as follows: S. bungeana > A. frigida > H. altaicus > L. davurica. The drought resistance ability of the different species was closely linked with vegetation succession from communities dominated by annual and biennial species (with main accompanying species of L. davurica and H. altaicus) to communities dominated by perennial species (S. bungeana and A. frigida) when soil became dry owing to increasing evapotranspiration after cropland abandonment. The restoration of S. bungeana steppe after cropland abandonment on the Ordos Plateau is recommended both as high‐quality forage and for environmental sustainability.

Response of Soil Respiration and Its Components to Nitrogen and Phosphorus Addition in Farming-Withdrawn Grassland in the Semiarid Loess Hilly-Gully Region

Understanding the soil respiration characteristics in response to nitrogen and phosphorus addition in farming-withdrawn grasslands within semi-arid loess hilly-gully regions is of great importance for providing a theoretical basis for evaluating the effects of artificial regulation approaches on carbon cycling. We report on a field experiment that was undertaken from May to September 2018 in a farming-withdrawn grassland ecosystem in China, which is dominated by Stipa bungeana and Lespedeza davurica. Three different levels of nitrogen and phosphorus additions were used, including three main plots of N[0, 50, and 100 kg·(hm2·a)-1] and three subplots of P (P2O5)[0,40, and 80 kg·(hm2·a)-1]. The soil respiration rate, heterotrophic respiration rate, soil temperature, and soil moisture were measured monthly in each treatment. Results showed that N and P addition had no effect on soil temperature or moisture content (P>0.05). The soil respiration rate showed an obvious monthly variation and peaked in July. In the treatment without fertilizer addition, the monthly mean soil respiration rate, heterotrophic respiration rate, and autotrophic respiration rate were 0.69, 0.39, and 0.29 g·(m2·h)-1, respectively. P addition had no significant effect on the soil respiration rate and its components without N addition (P>0.05). Under conditions of N addition, P addition significantly increased the soil respiration rate and its component (P<0.05). The monthly mean soil respiration rate, heterotrophic respiration rate, and autotrophic respiration rate were 0.93, 0.50, and 0.47 g·(m2·h)-1, respectively. The Q10 (i.e., temperature sensitivity) values for soil respiration, heterotrophic respiration, and autotrophic respiration in unfertilized soil were 1.86, 2.36, and 2.24, respectively. The addition of N and P reduced the Q10 value of soil respiration and its components. Our findings suggest that the response of soil respiration and its two components to N and P addition in studied farming-withdrawn grassland in the semiarid loess hilly-gully region were closely related to their addition amounts.

The Complete Chloroplast Genomes of Two Lespedeza Species: Insights into Codon Usage Bias, RNA Editing Sites, and Phylogenetic Relationships in Desmodieae (Fabaceae: Papilionoideae).

The genus Lespedeza (tribe: Desmodieae) consists of about 40 species that have high medicinal and economic value. However, in this genus, using morphological characters, the species identification is quite complicated, which can be solved by the analysis of the complete chloroplast genomes. As primary organelle genomes, the complete genome sequences of chloroplasts (cp) provide unique molecular information to study the divergence of species, RNA editing, and phylogeny. Therefore, to the best of our knowledge, for the first time, we sequenced the complete cp genomes of two representative Lespedeza species: Lespedeza davurica and Lespedeza cuneata. The cp genomes of both the species were found to be 149,010 bp in length, exhibiting the typical angiosperm chloroplast structure containing four regions. The Lespedeza cp genomes showed similar conserved gene contents, order, and orientations with a total GC content of 35.0%. A total of 128 genes, including 83 protein-coding genes, 37 tRNAs, and eight rRNAs, were identified from each genome. Unique molecular features of the two Lespedeza cp genome sequences were obtained by performing the analysis of repeats, sequence divergence, codon usage, and predicting the RNA editing sites in addition to phylogenetic analysis with other key genera in tribe Desmodieae. Using the two datasets, the phylogenetic relationship of Lespedeza species among Deasmodieae was discovered, suggesting that whole cp genomes provided useful information for phylogenetic studies of these species.

Responses of leaf functional traits of dominant plant species in grassland communities to nitrogen and phosphorus addition in loess hilly-gully region.

To analyze plant functional traits of dominant species to nitrogen and phosphorus addition, three species (Bothriochloa ischaemum, Stipa bungeana, and Lespedeza davurica) were selected in the loess hilly-gully region. A split-plot experiment which included three N treatments (0, 50, and 100 kg N·hm-2·a-1) and three P treatments (0, 40, and 80 kg P2O5·hm-2·a-1) was conducted. At the fast-growing stage, leaf length, leaf width, specific leaf area, leaf dry matter content, leaf N content, leaf P content, and leaf N:P were measured. Results showed that under 50 and 100 kg N·hm-2·a-1 treatments, leaf length and width of B. ischaemum increased significantly by 35.3% and 64.4%, respectively, while only the leaf length of S. bungeana and the leaf width of L. davurica increased significantly by 58.8% and 33.9%, respectively. Leaf dry matter content of the three species decreased significantly by 10.7%, 15.3% and 11.2%, respectively. Leaf N content and N:P of B. ischaemum and S. bungeana increased significantly by 23.0% and 99.2%, 45.8% and 96.9%, respectively, compared with unfertilized treatments. Under 40 and 80 kg P2O5·hm-2·a-1 treatments, leaf length, leaf width and specific leaf area of L. davurica increased significantly by 56.9%, 41.4% and 19.6%, respectively, while leaf dry matter content decreased significantly by 14.9%. Leaf P content of three species increased significantly by 96.7%, 110.9% and 238.4%, while the N:P decreased significantly by 45.8%, 42.8% and 53.7%, respectively, compared with those under unfertilized. Under 50 kg N·hm-2·a-1 treatment, compared with no P application, leaf length and leaf width of L. davurica and leaf P content of the three species significantly increased, and leaf N content of B. ischaemum and S. bungeana decreased significantly at 40 and 80 kg P2O5·hm-2·a-1 treatments. Under 100 kg N·hm-2·a-1 treatment, leaf length of B. ischaemum and S. bungeana, leaf width of L. davurica and leaf P content of three species significantly increased, while leaf N content of B. ischaemum decreased significantly after P application. In summary, functional traits of dominant species showed significant responses to short-term nitrogen and phosphorus addition, with the different responses were mainly related to species traits and fertilization levels. Such difference reflected plant adaptation to habitat changes. The divergent responses of different species to nitrogen and phosphorus addition played an important role in maintaining diversity and stability of grassland communities.

Using water isotopes to analyze water uptake during vegetation succession on abandoned cropland on the Loess Plateau, China

The Chinese government implemented the largest environmental recovery plan in the 1990s, the Grain for Green Project, on the Loess Plateau to prevent soil erosion. Extensive areas of cultivated land were abandoned and then gradually restored with communities of native vegetation. Little is known, however, about the successional development of these communities and their strategies of water use. We collected soil and root samples from four vegetation communities at different stages of succession (Artemisia capillaris, A. sacrorum, Bothriochloa ischaemum and Lespedeza davurica) in the dry and wet seasons of 2015 in the Wangmaogou watershed of the Wuding River. Both the root systems and soil-water contents tended to increase with successional development and fluctuated with changes of the dry and wet seasons. Isotopic analysis indicated that the thawing of winter snow during the dry season in April provided sufficient soil water. The vegetation communities only used the water in the 0–20 cm soil layer during the early successional stage. This range increased to 0–100 cm as the succession developed, with strong seasonal variation; water was accessed from deeper soil during the dry season, and water was accessed from shallower soil during the wet season. Antecedent rainfall, soil-water content and root distribution strongly influenced the use of water in all four vegetation communities. In the process of restoration and succession of vegetation communities, the behavior characteristics and water absorption strategies of the root system are the important theoretical basis for optimizing the selection of species and accelerating the speed of ecological restoration in Chinese Loess Plateau.

Responses of soil respiration to rainfall pulses in a natural grassland community on the semi-arid Loess Plateau of China

Pulsed rainfall affects both aboveground vegetation dynamics and belowground biogeochemical processes, such as carbon cycling, in semi-arid regions. In order to study carbon released by soil respiration (SR) after rainfall pulses in natural grassland on the Loess Plateau, a rainfall simulation experiment was conducted in a grassland community co-dominated by a C4 herbaceous grass [Bothriochloa ischaemum (L.) Keng] and a C3 leguminous subshrub [Lespedeza davurica (Laxm.) Schindl] in the loess hilly-gully region. Soil respiration rate (Rs), soil temperature (Ts), and soil volumetric water content (Sv) were measured 1 day before and 1, 2, 3, 5, and 7 days after four rainfall treatments (ambient rainfall plus a 5 mm, 10 mm, 20 mm, and 30 mm rainfall pulse) and one control treatment (only ambient rainfall) in June and August 2013. Results showed that Rs and Sv largely increased one day after simulated rainfall > 5 mm. In June, the peak Rs under 10, 20, and 30 mm rainfall was 0.80–1.03 μmol C m−2 s−1 in B. ischaemum, with a 25–62% increase compared with the control treatment, and 0.74–1.0 μmol C m−2 s−1 (+51–104%) in L. davurica. In August, the peak Rs was 1.23–1.73 μmol C m−2 s−1 (+23–73%) and 1.52–1.70 μmol C m−2 s−1 (+81–102%) in B. ischaemum and L. davurica, respectively. The magnitude and duration of the increase in SR were positively related to the rainfall size, and a more considerable increase was observed in August. There was a threshold rainfall (i.e., 5–10 mm) for triggering SR increases in both months. And different responses were found between the two species, there was more substantial SR increases in L. davurica in comparison to B. ischaemum. After rainfall pulses, soil moisture and soil temperature co-regulated SR. During the relatively dry season (i.e., June), SR was negatively correlated with soil temperature and the temperature sensitivity Q10 value of SR was small (0.5–0.6), while it changed to positively in August and the Q10 was largely increased (3.2–4.3). Conversely, soil moisture was positively related to SR in both months and explained a large portion of the variation in SR (32–43% and 42–52% in B. ischaemum and L. davurica, respectively). These findings indicated that soil moisture was the major environmental factor in controlling SR in this grassland. Overall, our study suggests that SR response following rainfall pulses is species-specific within the grassland community and tends to be controlled by soil moisture, and these should be considered in the regional carbon budget assessment in the background of vegetation rehabilitation and rainfall pattern changes.

Effects of interspecific competition on plant-soil feedbacks generated by long-term grazing

Grazing by large herbivores leads to changes in soil properties which can in turn modify plant performance. However, little is known about how competition among plant species alters the strength and direction of grazing-induced plant-soil feedbacks (PSFs). In a previous monoculture experiment, we found that the intensity of sheep grazing generated consistent abiotic feedback effects and species-specific biotic feedback effects. To test if and how interspecific plant competition modifies the PSFs observed in our previous monoculture experiment, five naturally-occurring plant species (Artemisia capillaris, Dodartia orientalis, Lespedeza davurica, Oxytropis racemosa, and Stipa bungeana) were grown in mixed communities in sterilized and unsterilized soils from plots of four grazing intensities (0, 2.7, 5.3, and 8.7 sheep/ha). Further, the five plant species were grown in mixtures in treatment-specific soil following inoculation with arbuscular mycorrhizal fungi (AM) and/or a mixture of pathogenic Fusarium species (FU), to test the contribution of these two fungal groups to biotic PSFs. All plant species experienced net neutral to positive abiotic and biotic PSFs. Compared with our previous monoculture experiment, we found that the presence of interspecific competition did not change the abiotic PSF effects generated with increasing grazing intensity, but shifted the direction and strength of the biotic PSFs generated within each grazing intensity. The presence of pathogenic Fusarium-only significantly decreased the proportional biomass of the dominant species A. capillaris and S. bungeana, and the presence of AM fungi-only significantly increased the proportional biomass of the subordinate species D. orientalis and O. racemosa. Our study strongly suggests that in grazed ecosystems interspecific competition and biotic PSFs interact to drive plant community dynamics, and also that soil mutualists such as AM fungi have the potential to promote plant species coexistence by facilitating the performance of subordinate species.

Soil Moisture Availability at Early Growth Stages Strongly Affected Root Growth of Bothriochloa ischaemum When Mixed With Lespedeza davurica.

Rainfall is the main resource of soil moisture in the semiarid areas, and the altered rainfall pattern would greatly affect plant growth and development. Root morphological traits are critical for plant adaptation to changeable soil moisture. This study aimed to clarify how root morphological traits of Bothriochloa ischaemum (a C4 herbaceous species) and Lespedeza davurica (a C3 leguminous species) in response to variable soil moisture in their mixtures. The two species were co-cultivated in pots at seven mixture ratios under three soil water regimes [80% (HW), 60% (MW), and 40% (LW) of soil moisture field capacity (FC)]. At the jointing, flowering, and filling stages of B. ischaemum, the LW and MW treatments were rewatered to MW or HW, respectively. At the end of growth season, root morphological traits of two species were evaluated. Results showed that the root morphological response of B. ischaemum was more sensitive than that of L. davurica under rewatering. The total root length (TRL) and root surface area (RSA) of both species increased as their mixture ratio decreased, which suggested that mixed plantation of the two species would be beneficial for their own root growth. Among all treatments, the increase of root biomass (RB), TRL, and RSA reached the highest levels when soil water content increased from 40 to 80% FC at the jointing stage. Our results implied that species-specific response in root morphological traits to alternated rainfall pattern would greatly affect community structure, and large rainfall occurring at early growth stages would greatly increase their root growth in the semiarid environments.

Accumulation of N and P in the Legume Lespedeza davurica in Controlled Mixtures with the Grass Bothriochloa ischaemum under Varying Water and Fertilization Conditions.

Water and fertilizers affect the nitrogen (N) and phosphorus (P) acquisition and allocation among organs in dominant species in natural vegetation on the semiarid Loess Plateau. This study aimed to clarify the N and P accumulation and N:P ratio at organ and plant level of a local legume species mixed with a grass species under varying water and fertilizer supplies, and thus to fully understand the requirements and balance of nutrient elements in response to growth conditions change of native species. The N and P concentration in the organ (leaf, stem, and root) and plant level of Lespedeza davurica (C3 legume), were examined when intercropped with Bothriochloa ischaemum (C4 grass). The two species were grown outdoors in pots under 80, 60, and 40% of soil water field capacity (FC), -NP, +N, +P, and +NP supply and the grass:legume mixture ratios of 2:10, 4:8, 6:6, 8:4, 10:2, and 12:0. The three set of treatments were under a randomized complete block design. Intercropping with B. ischaemum did not affect N concentrations in leaf, stem and root of L. davurica, but reduced P concentration in each organ under P fertilization. Only leaf N concentration in L. davurica showed decreasing trend as soil water content decreased under all fertilization and mixture proportion treatments. Stems had the lowest, while roots had the highest N and P concentration. As the mixture proportion of L. davurica decreased under P fertilization, P concentration in leaf and root also decreased. The N concentration in L. davurica at the whole plant level was 11.1–17.2%. P fertilization improved P concentration, while decreased N:P ratio in L. davurica. The N:P ratios were less than 14.0 under +P and +NP treatments. Our results implied that exogenous N and P fertilizer application may change the N:P stoichiometry and influence the balance between nutrients and organs of native dominant species in natural grassland, and P element should be paid more attention when considering rehabilitating degraded grassland via fertilization application in semiarid Loess Plateau region.